Seaboard F3s

I am interested in modeling the ACL-SAL in 1957-59 timeframe. I know the differences in ACL units, but not Seaboard. I know (through photo evidence) that SAL F3s had received extra grab irons by 1959 and skirts were being removed. In Langley's SAL album on page 126 it shows the 4028 with full skirt, mu connections but no handrails.

My questions are - when did SAL add mu connections? Did they add the grab irons before 1959 (I know this was an FRA requirement)?

I want to paint a Stewart F3 as SAL 4028 but need these answered before I have it done.

Answers

The extra grab irons were an Interstate Commerce Commission
requirement made around 1955 or so. (There was no Federal Railroad
Administration until 1967, when the Department of Transportation
assumed the safety functions of the ICC.) The exact date of the
order I do not know, nor do I know what kind of compliance window was
established, so I cannot tell you the exact date of the installation
of these devices, but circa 1955 would be close, I think.